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CVE-2026-69204— Http4s: Ember accepts Transfer-Encoding combined with Content-Length (CL.TE request smuggling)

Quick assessment

Affected
http4s http4s
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Http4s 是用于 HTTP 服务的 Scala 接口。在 0.23.35 和 1.0.0-M47 之前，Ember HTTP/1.1 实现不会拒绝同时包含 和 头部的消息，导致中间代理服务器和 Ember 可能采用不同的请求体分帧规则。当 ember-server 位于一个启用 keep-alive 的中间代理之后，且该代理同时转发了这两个头部并基于 进行分帧时，未经身份验证的攻击者可以实施“请求走私”（Request Smuggling）：向服务器发送一个第二请求，从而绕过中间代理的访问控制、污染缓存，或者使

CVSS 9.2 · Critical

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 2

VendorProduct Version RangeStatus
http4s http4s < 0.23.35 affected
>= 1.0.0-M1, < 1.0.0-M47 affected
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I. Basic Information for CVE-2026-69204

Vulnerability Information
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Vulnerability Title
Http4s: Ember accepts Transfer-Encoding combined with Content-Length (CL.TE request smuggling)
Source: CVE Program / CVE List V5
Vulnerability Description
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember HTTP/1.1 does not reject messages containing both Transfer-Encoding and Content-Length, so an intermediary and Ember can select different body framing rules. When ember-server is behind a keep-alive intermediary that forwards both headers and frames by Content-Length, an unauthenticated attacker can smuggle a second request, bypass intermediary access controls, poison caches, or cause a victim request to be joined to an attacker-controlled prefix. The shared response parser can also desynchronize an ember-client connection when a malicious or compromised upstream sends both headers. This issue is fixed in versions 0.23.35 and 1.0.0-M47.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
HTTP请求的解释不一致性(HTTP请求私运)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
http4s http4s < 0.23.35 -

II. Public POCs for CVE-2026-69204

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III. Intelligence Information for CVE-2026-69204

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Patches & Fixes for CVE-2026-69204 (1)

Vendor Advisories for CVE-2026-69204 (1)

Vendor Pages for CVE-2026-69204 (2)

Same Patch Batch · http4s · 2026-09-15 · 18 CVEs total

CVE-2026-69217 8.7 HIGH Http4s: Ember Server accepts duplicate Content-Length headers
CVE-2026-69205 8.7 HIGH Http4s: Ember Transfer-Encoding value parsing (TE.CL / TE.0 request smuggling)
CVE-2026-88975 7.5 HIGH Http4s: Ember HTTP/2 buffers a frame's declared payload before checking SETTINGS_MAX_FRAME
CVE-2026-69208 7.5 HIGH Http4s: DigestAuth nonce map grows unbounded
CVE-2026-69202 7.5 HIGH Http4s Ember HTTP/2: unbounded inbound body buffering
CVE-2026-69218 7.5 HIGH Http4s Ember HTTP/2: unbounded continuation frame accumulation
CVE-2026-69210 7.5 HIGH Http4s: WebSocket decoder accepts negative length, causing infinite decode loop
CVE-2026-69213 7.5 HIGH Http4s Ember HTTP/2: unbounded outbound frame queue
CVE-2026-69203 7.5 HIGH Http4s Ember HTTP/2: does not enforce SETTINGS_MAX_CONCURRENT_STREAMS
CVE-2026-69209 7.5 HIGH Http4s: WebSocket decoder accepts unbounded message sizes
CVE-2026-69214 6.8 MEDIUM Http4s: CookieJar middleware accepts arbitrary Set-Cookie domain
CVE-2026-69215 6.8 MEDIUM Http4s: CookieJar middleware matches by substring, leaking cookies cross-origin
CVE-2026-69201 5.9 MEDIUM Http4s: ResourceService and Webjar Service path escape via percent-encoded separators
CVE-2026-69212 5.9 MEDIUM Http4s: FollowRedirect middleware leaks credentials over https->http same-authority redire
CVE-2026-69206 5.9 MEDIUM Http4s: DigestAuth allows replay of captured requests
CVE-2026-69216 5.4 MEDIUM Http4s: Ember chunk parser lenience (TE.TE request smuggling)
CVE-2026-69211 4.8 MEDIUM Http4s: Set-Cookie rendering does not escape attribute delimiters

IV. Related Vulnerabilities

Same product: http4s
Same vendor: http4s
Same weakness: CWE-444

V. Comments for CVE-2026-69204

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